Side-On Sulfur Monoxide Complexes of Tantalum, Niobium, and Vanadium Oxyfluorides

Abstract

Side-on sulfur monoxide complexes of tantalum, niobium, and vanadium oxyfluorides OMF 2 (η 2 -SO) were prepared via the reactions of metal atoms and SO 2 F 2 upon UV−vis irradiation in a cryogenic matrix. The product structures were identified by the characteristic infrared absorptions and isotopic frequency ratios of terminal M−O, F−M−F, and M−(SO) stretches, which were further supported by density functional theory calculations at the B3LYP level. All of the three complexes were predicted to have doublet ground states with the S−O bond nearly perpendicular to the terminal metal−oxygen bond. Although end-on bonded isomers with either M−OS or M−SO geometry are stable as well, they are higher in energy than the side-on isomers, and their vibrational frequencies do not match the experimental values. For the OMF 2 (η 2 -SO) complexes, the S−O bond length approaches that of SO − , but it is longer than that of neutral SO due to the electron transfer from the metal d orbital to the in-plane π* orbital of SO. The metal−SO bonding in the side-on complex is mainly ionic, but covalent interactions play some role between the two parts. On the basis of the calculation results, the OMF 2 (η 2 -SO) complexes can be considered as (OMF 2 ) + (SO) − in which the unpaired electron is mainly located in the out-ofplane π* orbital of SO. In addition to the complexes containing SO ligand, a series of other stable isomers were obtained by the B3LYP calculations, and they were proposed as intermediates involved in the formation of the OMF 2 (η 2 -SO) products via fluorine and oxygen transfer reactions between metal atoms and SO 2 F 2 under UV−vis irradiation.

Preparation of Group 3 Metal Sulfur Monoxide Complexes via Oxidation of Metal Atoms using SOF2 in Cryogenic Matrixes

“…This is about 0.1 Å longer than that of neutral SO molecule (1.488 Å) but close to those of the SO ligands of group 5 OMF 2 (η 2 -SO) complexes (~1.59 Å) predicted at the same level of theory that feature a superoxo-like character. [19] This is consistent with the fact that the calculated SÀ O stretching vibrational frequencies of ScF 2 (η 2 -SO), YF 2 (η 2 -SO) and LaF 2 (η 2 -SO) are closer to those of group 5 OMF 2 (η 2 -SO) complexes and diatomic SO À (894.9 cm À 1 ), [19] and the experimental frequencies are significantly lower than neutral SO (1136.7 cm À 1 ) molecule. [24] Both bond lengths and vibrational frequencies demonstrate that the SO ligand in ScF 2 (η 2 -SO), YF 2 (η 2 -SO) and LaF 2 (η 2 -SO) is close in nature to SO À , and these complexes can be described as [(MF 2 ) + (SO) À ].…”

“…[15][16][17] In particular, sulfur monoxide complexes were obtained in some cases as long as there are enough valence electrons from the metal center to support one SO and one oxo ligand as well as two fluoro ligands. [18,19] The reactions of molybdenum and tungsten atoms with SO 2 F 2 in solid matrixes gave rise to side-on OMoF 2 (η 2 -SO) and OWF 2 (η 2 -SO), which are considered as peroxo-like metal complexes, (OMoF 2 ) 2 + (SO) 2À and (OWF 2 ) 2 + (SO) 2À . [18] Although the group 5 metal-sulfur monoxide complexes OMF 2 (η 2 -SO) (M = V, Nb, Ta) prepared in the same way possess similar geometries, the sideon SO ligand is better described as a superoxo-like ligand (SO) À according to the SO stretching vibrational frequency and bond length.…”

“…[18] Although the group 5 metal-sulfur monoxide complexes OMF 2 (η 2 -SO) (M = V, Nb, Ta) prepared in the same way possess similar geometries, the sideon SO ligand is better described as a superoxo-like ligand (SO) À according to the SO stretching vibrational frequency and bond length. [19] The end-on oxygen-bound coordination mode was identified in the OTiF 2 (η 1 -OS) complex that was formed upon isomerization of a bidentate sulfur dioxide complex of titanium difluoride under UV-vis irradiation, but the interaction between OTiF 2 and OS is quite weak. [20] The situation is quite different for group 3 metals, and only bidentate sulfur dioxide complexes in the form of ScF 2 (O 2 S), YF 2 (O 2 S) and LaF 2 (O 2 S) were obtained from the reactions of metal atoms and SO 2 F 2 .…”

Reactivity of Small Oxoacids of Sulfur

“…For synthetic purposes in organic chemistry, sulfur monoxide can be received in situ, for example, from thiirane oxide [82] or a trisulfide-2-oxide [83]. SO can be trapped by dienes or metal complexes [84,85,86,87]. Thus, heating trisulfide oxide (1) in the presence of dienes (2) results in transfer of sulfur monoxide to form cyclic unsaturated sulfoxides (3) in good to excellent yields, along with recovery of disulfide (4) (Scheme 4) [83].…”

Reduction of Sulfur Dioxide to Sulfur Monoxide by Ferrous Porphyrin

“…7 Most of these approaches require H2/CO gas, high temperatures and supporting metal oxide heterogeneous catalysts. [8][9][10][11] Although there are some examples of transition metal complexes with bound SO2 and SO, [12][13][14][15][16][17] reduction of SO2 by molecular systems are rare and needs to be explored to marshal newer methods for SOx valorization. 18 A host of microbial organisms recycle SOx as a part of the geochemical Sulfur cycle and, recently, these organisms have been used to valorize sulfur from alkaline extract of flue gas which contains SO2.…”